Rusty Tussock Moths

Here at Pacific Science Center, our Life Sciences staff has quite a bit of experience working with butterflies. One might think that after operating our Tropical Butterfly House for over 14 years butterflies and moths aren’t particularly exciting or novel to us. Not so! Recently, we took part in an occurrence that we rarely get to see: a full life cycle of a moth.

Pacific Science Center’s permits only allow us to deal with the pupa and adult stages of Lepidoptera life cycles. However, such restrictions don’t apply to local fauna. So when Life Sciences Manager Sarah Moore’s family discovered some caterpillars right outside the gates of PSC, Caretaker Chris Russell jumped at the chance to collect them. These caterpillars were the larval stage of the Rusty Tussock moth, Orgyia antiqua.

The caterpillars were quickly installed into an exhibit with leaves similar to the host plant they were munching on outside. They quickly went to work. Before long, the caterpillars had significantly grown in size and some had even started to pupate. Moths are cocoon builders and pretty soon, silky cases were all over the exhibit.

Here’s where things get interesting for this species of moth. While typical Lepidoptera reach adulthood, emerge from a cocoon or chrysalis and fly off to find a mate, the female Rusty Tussock moth has no such option. Her adult form is completely flightless. She just hangs out next to her cocoon, releases some pheromones, and waits for a flying male to find her. Our males and females both emerged, found each other, and soon enough there was a nice little pile of eggs lying next to each female.

The life cycle of this moth is very seasonal. The eggs overwinter and don’t emerge until the following spring. So our short-lived exhibit gave us a chance to see a bit more of a moth life cycle and explore an interesting reproductive strategy. But it won’t be interesting year round. Waiting ten months for eggs to hatch is right up there with watching paint dry on the list of exciting exhibit options.

And while this moth is found locally, it isn’t a native species. The Rusty Tussock moth is native to Europe and somehow made their way out to the Western United States. While not invasive, the caterpillars are sometimes considered a pest for local flora. Removing them from the habitat doesn’t impact wildlife or hurt the environment. Therefore, we are not going to try raising a new generation in captivity. We will simply collect more next year.

For a short while, we can observe a few moths flying on exhibit and some females laying their eggs. And because summertime in the Pacific Northwest includes a variety of interesting arthropods, we’ll soon be featuring some spiders, clown millipedes and other amazing animals that call this area their home. Stop by and check them out!